Bone and Soft Tissue Infections Flashcards by Chloe Mackle

What are the types of osteomyelitis?

Acute, subacute or chronic

Specific or non-specific

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In what people is acute osteomyelitis most common?

Mostly children, boys > girls

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What is the acute osteomyelitis associated with?

History of minor trauma 
Diabetes
Rheumatoid arthritis 
Immune compromise 
Long-term steroid treatment 
Sickle cell disease

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What are the modes of spread of acute osteomyelitis?

Haematogenous spread in children and elderly
Local spread from contiguous site of infection e.g. trauma

Infants - infected umbilical cord
Children - boils, tonsillitis, skin abrasions
Adults - UTI, arterial line

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What is the most common causative organism of acute osteomyelitis?

Infants < 1 - staph aureus, followed by group B strep, then E. coli

Older children - staph aureus, followed by streptococcus pyogenes then haemophilus influenzae

Adults - staph aureus, followed by coagulase negative staph, propionibacterium spp., strep pyogenes, mycobacterium tuberculosis etc.

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What is commonly the causative organism of acute osteomyelitis in butchers?

Brucella

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What is commonly the causative organism of acute osteomyelitis in fishermen and filleters?

Mycobacterium marium

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In what patients is candida more commonly a causative organism of acute osteomyelitis?

Debilitating illness 
HIV/AIDS
Long-term antibiotic treatment 
GI surgery 
Malignancy

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What are the special cases of acute osteomyelitis where causative organisms would be different from the normal population?

Diabetic foot and pressure sores - mixed infection, including anaerobes
Vertebral osteomyelitis - staph aureus, TB
Sickle cell disease - salmonella species
STD - gonococcus

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What is the pathology of acute osteomyelitis?

Starts at metaphysis
Vascular stasis
Acute inflammation causing increased pressure
Suppuration
Release of pressure (medulla, sub-periosteal, into the joint)
Necrosis of bone (sequestrum)
New bone formation (involucrum)
Resolution or no resolution and development into chronic osteomyelitis
Septic arthritis in the bone can also develop, most commonly in the hip and elbow

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What is infected in acute osteomyelitis of long bones?

Metaphysis infected e.g. distal femur, proximal tibia, proximal humerus

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What are the clinical features of acute osteomyelitis in infants?

Signs can range from minimal to severe illness
Failure to thrive
Drowsy or irritability 
Can be minimal signs or very systemically unwell
Metaphyseal tenderness and swelling 
Reduced range of movement 
Positional change 
Commonest around the knee

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What are the clinical features of acute osteomyelitis in children?

Severe pain
Reluctant to move - not weight bearing 
May be tender, fever and tachycardia
Malaise - fatigue, nausea and vomiting 
Toxaemia

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What are the clinical features of acute osteomyelitis in adults?

Primary OM seen in thoracolumbar spine
Backache
History of UTI or urological procedure
Elderly, diabetic or immunocompromised
Unremitting pain - keeping patient awake at night

Secondary OM much more common
Often after open fracture or surgery
Mixture of causative organisms

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Why do you need to be particularly aware of wounds that fail to heal and are likely to be infected that are close to the bone?

Because all of the necrotic tissue will need to be derided - both soft tissue and bone

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What investigations should be done if suspecting acute osteomyelitis?

FBC and WBC - neutrophil leucocytosis
ESR
CRP
Blood cultures 3x at peak temperature, 60% positive
U&Es - ill, dehydrated
X-ray - not useful in acute presentation, can take 1-2 weeks to show, shows metaphyseal destruction at later dtage
US - more useful in hip if infection is in the joint
Aspiration
Isotope bone scan - non-specific
Labelled white cell scan - non-specific

MRI is the best investigation - accurate and good for determining the extent of infection

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What are the differential diagnoses for acute osteomyelitis?

Acute septic arthritis
Trauma
Acute inflammatory arthritis
Transient synovitis

Rare - sickle cell disease, Gaucher’s disease, rheumatic fever, haemophilia

Soft tissue infection - cellulitis, erysipelas, necrotising fasciitis

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What would be seen on the radiographs of a patient with acute osteomyelitis?

X-ray will be normal in first 10-14 days
Later will show increasing metaphyseal destruction
Early radiographs will show minimal changes
Early periosteal changes happen 10-20 days
Medullary changes occur in lytic areas
Late osteonecrosis - sequestrum
Late periosteal new bone - involucrum

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What scans might be done for acute osteomyelitis?

Technetium-99m labelled bisphosphonate
Gallium 67 citrate delayed imaging
Indium-111 labelled WBC scan
MRI

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What microbiology is done for acute osteomyelitis?

Blood cultures in haematogenous osteomyelitis and septic arthritis
Bone biopsy
Tissue or swabs from up to 5 sites around implant at debridement in prosthetic infections
Sinus tract and superficial swab results may be misleading due to skin contaminant

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What is the treatment of acute osteomyelitis?

Supportive for pain and dehydration
Rest
Splintage
Antibiotics - IV/oral switch 7-10 days, 4-6 week duration oral antibiotics depending on response and ESR
Empirical antibiotics while waiting for cultures - flucloxacillin and benzylpenicillin

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What does antibiotic choice depend on?

Spectrum of activity
Penetration to bone
Safety of long-term administration

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Why might antibiotic failure occur?

Drug resistance e.g. beta-lactamases
Bacterial persistence e.g. dormant bacteria in dead bone
Poor host defences - diabetes, alcoholism
Poor drug absorption
Poor tissue perfusion
Drug inactivation by host flora
MRSA

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What are the indications for surgery for acute osteomyelitis?

Aspiration of pus for diagnosis and culture
Abscess drainage - multiple drill holes, primary closure to avoid sinus
Debridement of dead/infected/contaminated tissue
Refractory to non-operative treatment > 24-48 hours - timing, drainage, lavage, infected joint replacements

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What are the potential complications of acute osteomyelitis?

``` Septicaemia Death Metastatic infection Pathological fracture Septic arthritis Altered bone growth Chronic osteomyelitis ```

When does subacute osteomyelitis occur?

Increased host resistance Lowered bacterial virulence Antibiotic usage

What are the clinical features of subacute osteomyelitis?

Long history - weeks to months Variable symptoms - pain, limp Local swelling, occasionally warmth Tenderness

What are the differential diagnoses for subacute osteomyelitis?

Tumour e.g. Ewing's sarcoma, osteoid osteoma | TB

What are the features of Brodie's abscess?

Subacute osteomyelitis Older children Painful limp, no systemic features Radiographic lucency in long bone metaphysis

What are the differential diagnoses for Brodie's abscess?

Ewing's sarcoma

What are the investigations for subacute osteomyelitis?

X-ray Bone scan Biopsy - 50% positive Grow organism

What is the treatment of subacute osteomyelitis?

Curettage | Prolonged antibiotics

When does chronic osteomyelitis occur?

May follow acute osteomyelitis Much rarer in children May start de-novo following an operation or open fracture, or in a patient with immunocompromise e.g. diabetes, elderly

What are the features of chronic osteomyelitis?

Repeated breakdown of healed wounds Often mixed infection Usually the same causative organism at each flare-up Cavities, possible sinuses Dead bone - retained sequestra Involucrum Histological picture of chronic inflammation

What are the most common causative organisms of chronic osteomyelitis?

Staph aureus still most common E. coli Strep pyogenes Proteus

What is the treatment of chronic osteomyelitis?

``` Long-term antibiotics - local and/or systemic Eradicate bone infection surgically Treat soft tissue problems Deformity correction Massive reconstruction Amputation ```

What are the potential complications of chronic osteomyelitis?

Chronically discharging sinus and flare-ups Ongoing infection - metastatic, abscesses Pathological fracture Growth disturbance and deformities SCC in 0.07%

What is acute septic arthritis?

Infection in a joint

What are the modes of infection that cause acute septic arthritis?

Direct invasion from penetrating wound, intra-articular injury or arthroscopy Eruption of bone abscess Haematogenous spread Metaphyseal septic focus - either septic arthritis or osteomyelitis

What are the most common causative organisms of acute septic arthritis?

Staphylococcus aureus most common Strep pyogenes Haemophilus influenzae E. coli

What is the pathology of acute septic arthritis?

Acute synovitis with purulent joint effusion Articular cartilage attacked by bacterial toxin and cellular enzyme Complete destruction of the articular cartilage

What are the possible sequelae of acute septic arthritis?

Complete recovery Partial loss of articular cartilage and subsequent OA Fibrous or bony ankylosis

What are the features of acute septic arthritis in neonates?

Picture of septicaemia Irritability Resistant to movement - more painful than acute osteomyelitis due to build-up of pressure Systemically unwell

What are the features of acute septic arthritis in children?

Acute pain in a single joint Reluctant to move the joint in any way, consider bursitis where range of movement is normal Increased temperature and pulse Increased tenderness

What are the features of acute septic arthritis in adults?

Often involves a superficial joint | Rare in healthy adults

What are the investigations that should be done for acute septic arthritis?

``` FBC WBC ESR CRP Blood cultures X-ray US Aspiration ```

What is the most common cause of acute septic arthritis in adults?

Infected joint replacement

What are the complication of acute septic arthritis in adults?

Death Amputation Removal of arthroplasty

What is the most common causative organism of acute septic arthritis in adults?

Staph aureus

What are the differential diagnoses for acute septic arthritis?

``` Acute osteomyelitis Trauma Pseudogout Irritable joint Haemophilia Rheumatic fever Gout Gaucher's disease ```

What is the treatment of acute septic arthritis?

General supportive Antibiotics 3-4 weeks Surgical drainage and lavage - arthroscopic lavage or open operation in infected joint replacements, followed by antibiotics

What is tuberculosis of bones and joints due to?

Used to be due to TB, rickets and polio | Now due to trauma and degenerative joint disease

What is the typical presentation of tuberculosis of bones and joints?

Bent children - unable to stand straight Thoracic kyphosis Lower limb deformities

What are the classifications of tuberculosis of bones and joints?

Extra-articular - epiphyseal/bones with haemodynamic marrow Intra-articular - large joints Vertebral body - most common Multiple lesions in 1/3rd

What are the clinical features of tuberculosis of bones and joints?

``` Insidious onset with general ill health Contact with TB Pain, especially at night Swelling Weight loss Low grade pyrexia Joint swelling Decreased range of movement (won't be seen in spine) Ankylosis Deformity ```

What is the pathology of tuberculosis of bones and joints?

Primary complex in lung or gut Haematogenous secondary spread to bones Tuberculous granuloma Role of nutrition and influence of other diseases e.g. HIV, AIDS

What is the presentation of spinal tuberculosis?

Little pain | Abscess or kyphosis

How is TB of bones and joints diagnosed?

``` Long history Involvement of a single joint Marked thickening of the synovium Marked muscle wasting Periarticular osteoporosis ```

What investigations should be done for TB of bones and joints?

``` FBC ESR Mantoux tests Sputum/urine culture X-ray Joint aspiration and biopsy - AAFB identified in 10-20%, culture +ve in 50% ```

What are the features of the x-ray of a patient with TB of bones/joints?

Soft tissue swelling Peri-articular osteopaenia Articular space narrowing

What are the differential diagnoses for TB of bones and joints?

Transient synovitis Monoarticular rheumatoid arthritis Pyogenic arthritis Haemorrhagic arthritis

What is the treatment of TB of bones and joints?

Chemotherapy Rifampicin, isoniazid, ethambutol and pyrazinamide - 8 weeks, followed by rifampicin and isoniazid for 6-12 months Rest and splintage Operative drainage rarely necessary